1. Field of the Invention
This invention relates to the manufacture of large scale display devices, and more particularly, the manufacture of large scale display devices by the stepping and scanning projection of images from a mask onto a plate.
2. Description of the Related Art
In recent years, there have been advances in the enlargement of the picture surface of display devices (made with glass plates) with a built-in liquid crystal display device or plasma display device. Mass produced articles having a display region of about 30-40 inches are being produced, with a future prospect of 60-inch wall mount type display devices having a width to height (aspect) ratios of 16:9. Further, for the production of printed circuit boards (ceramic plate, epoxy plate, high-molecular film sheet, and the like) of mother boards or CPU sub-boards used in electrical products to mount larger electronic devices, there is a need to both make the line width of the wiring patterns finer in order to increase the mounting density, and enlarge the boards.
Generally, photolithography is used to manufacture the fine circuit patterns for the display cells or wiring used for display panels, and is also used to manufacture the printed circuit boards used for electrical devices. The central role in the photolithography process is the need for an accurate exposure device to transfer an image of the circuit pattern on a mask to a resist (i.e., a plate coated with a substrate of uniform thickness on a glass plate or printed circuit board).
Conventional solutions using various exposure devices and exposure procedures have developed to transfer large circuit pattern structures onto glass plates or printed circuit boards. Among these solutions, picture surface stitch exposure methods have attracted attention. For these methods, the circuit patterns from the mask are joined on the substrate.
One such picture surface stitch exposure method is described in Japanese Unexamined Patent Publication JP-A-S62-145730 (U.S. Pat. No. 4,748,478). According to this method, a projection exposure device (stepper) is equipped with a high resolution projection lens, a mask (reticle) is divided into multiple circuit pattern regions, and a plate (substrate) to be exposed is on a stage. The projection exposure device moves/steps the stage to join the projected circuit pattern images on the substrate.
A similar known stepper type of exposure method is disclosed in JP-A-H1-161243 (U.S. Pat. No. 4,769,680). This method uses two high resolution projection lenses at fixed intervals. These lenses simultaneously expose the circuit pattern of masks installed in the respective projection lenses onto the plate, and join each respective projected image to the two circuit patterns on the preceding exposed substrate.
However, when forming large circuit pattern regions, such as those used for a display device, it is necessary to join images of multiple circuit patterns on a substrate. To accomplish this, methods, such as that disclosed in WO 95/16276, JP-A-H9-1909624 (U.S. Pat. No. 5,888,676), use stitch portions of respective circuit pattern images to make continuous boundaries (straight lines, polygonal lines, wavy lines, rectangles and the like). However, when there is a large difference in contrast of the stitch portions, this results in this boundary being visually observed, which is a disadvantage of this method.
For example, when exposing two respective circuit pattern images to be adjacently stitched onto a substrate using conventional methods, the gate width and the like of transistors used for driving color elements formed in the circuit pattern regions (display regions) differ minutely in the circuit patterns. This difference is due to residual alignment errors, residual focus errors, exposure amount control accuracy, and even differences in the drive voltage. This difference causes the transparency of the liquid crystal pixels to differ slightly in the resulting display regions.
To solve this problem, a method of gradation of the boundary line of the stitch portion has been developed as disclosed in JP-A-H6-324474. According to this method, a predetermined width in the stitch portion of the display portion is set within the circuit pattern, and the width is divided in a random stepping-stone form of interfitting relationship. By this method, without making a clear boundary line in the stitch portion, the combination of the fine pattern having a predetermined width and granularized as a whole is joined in an interfitting state.
The manufacture of circuit devices and display devices having display regions is possible by the various stitch exposure methods of the prior art. However, when taking the cycle time into account, they are not practical stitch exposure methods. For a liquid crystal device, because repeated stitch exposure of the mask pattern is possible in order to expose a display device, it is not necessary to change the mask frequently. However, when exposing the peripheral circuit portions of the display region (end portion pattern), the mask pattern must be frequently changed, and this changeover time increases the overall manufacturing time.
Of course, if the whole of the display region and the peripheral circuit portions are placed, unaltered, on one large mask that is larger than the external dimensions of the display device, it is possible to form the whole circuit pattern for the display device on the substrate without either exchanging the mask and stitch exposure. Nevertheless, in order to manufacture a device that has a size of 30-60 inches, a mask of the same size is necessary, and this makes the production of the mask difficult. In addition, as the size of the exposure device increases, the production of the mask becomes worse, particularly the mask stage unit.
Consequently, the present invention has as its object to provide a method of manufacturing a large circuit device or display device without a pronounced stitch mark by processing the arrangement or configuration of circuit patterns formed in a mask.
Another object of the present invention is to provide a method of manufacturing a large size circuit device or display device, while reducing the number of masks which are necessary during mask exposure.
Yet another object of the invention is to obtain a large size display device based on performing a smaller number of scans using a scanning exposure device.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
In an embodiment of the present invention, a method of manufacture of a circuit device comprises exposing the substrate while causing the relative positional relationship of the mask and plate to change so that circuit pattern regions on the mask are transferred with mutual stitching onto the plate for use in circuit device formation, and within the peripheral region of the circuit pattern region of the mask, respectively formed pattern counterparts of a pair of stitch regions (SA1, SSA2) are facing each other in the direction in which the relative positional arrangement is changed so as to form a mutually complementary interfitting relationship after exposure, and exposing the substrate while the relative changing positional arrangement to transfer both sides or one side of the pair of stitch regions on the mask and causing them to join in an interfitting state with the similar stitch region of the circuit pattern region periphery already transferred onto the plate.
In another embodiment of the present invention, within the pair of stitch regions the stitch regions comprise a repetitively formed fine pattern structure at predetermined intervals with respect to the direction in which the relative positional relationship is caused to change.
In another embodiment of the present invention, the configuration or arrangement of respectively formed pattern counterparts of the pair of stitch regions are made in a mutually complementary random interfitting relationship.
In another embodiment of the present invention, a minimum unit making the mutually complementary random interfitting relationship is determined to make a repetitively formed fine pattern structure at predetermined intervals.
In another embodiment of the present invention, a circuit device is a display portion of the display device with the minimum unit is a pixel.
In another embodiment of the present invention, each pixel has three pixel cell units corresponding to the three colors used in color display and, the fine pattern structure of the minimum unit comprising the mutually complementary random intermitting relationship was set in the pixel cell units.
In another embodiment of the present invention, each pixel of the display portion has three pixel cell units corresponding to the three colors, red, green and blue, for color display use, the complementary interfitting arrangement between pairs of stitch regions was made with the minimum unit being the division pattern elements divided by the number of pixel cell units, and arraying the division pattern elements in random stepping-stone form with respect to the direction in which the relative positional arrangement is caused to change.
In another embodiment of the present invention, the width in the direction in which the respective relative positional relationship of the pair of stitch regions is caused to change is determined according to a contrast difference (gradation difference) between two adjoining display regions formed by stitch exposure onto the plate.
In another embodiment of the present invention, a method of forming a large two-dimensional display device on a plate comprises stitch exposing circuit patterns formed on a mask onto a plate, where the circuit pattern formed on the plate is a laminated structure with mutually positionally united plural layers, and where the form of a first joint arising during stitch exposing the circuit pattern on the first N-th layer mask onto the plate or the configuration state of the circuit pattern on the first mask exposed within stitch regions differs from that of the second joint stitch exposed from the circuit pattern on the adjacent layer mask for the adjacent layers on the plate.
In a further embodiment of the present invention, the stitch regions are the multiples of the same circuit counterpart formed on the mask, or, when stitch exposing different circuit pattern counterparts onto the plate, are the overlapping portions of the stitch portions have a predetermined width, where the envelope curve joining the outer edges of the circuit patterns exposed within the stitch regions on the mask are a periodic waveform (i.e., an undulating line, triangular wave, rectangular wave) on the mask for use in forming the one layer, and making the waveforms a random polygonal line on adjacent layer masks, causing the configuration of the joint to differ between layers.
In another embodiment of the present invention, the amplitude of the envelope curve of the circuit pattern outer edge formed as a continuous periodic waveform or random polygonal line is the same as the width of the overlap of the stitch regions.
In another embodiment of the present invention, by stitch exposing circuit pattern counterparts formed on single or plural masks within the stitch regions onto the plate, where the peripheral region counterparts of circuit patterns to be stitched overlap by a predetermined width, the circuit patterns within these stitch regions are divided into pattern elements by randomly distributing, forming, and placing the divided pattern elements in respective peripheral regions of the circuit patterns on the masks to be stitch exposed, the configuration circuit patterns on the masks exposed within stitch regions on the plate differs between layers.
In another embodiment of the present invention, a method comprising sequentially projecting exposures where regions on the plate formed from a rectangular pattern region on the mask are mutually connected, and forming a large two-dimensional display device on the plate by moving the mask and the plate with respect to a projection system relative to a long side direction of the rectangular pattern region on the mask, stitch exposing a first image of the rectangular pattern region onto the plate, changing the relative position of the mask and plate relative to a short side direction of the rectangular pattern region on the mask positioning the mask and plate such that a second image of the rectangular pattern region is joined to the first image by stitch exposure, and the display region formed on the plate is formed in the rectangular pattern using a horizontal scan line in the direction at perpendicular to the direction of the scanning movement.
In another embodiment of the present invention, the two-dimensional display device has drive signal lines providing individual drive signals of each display pixel, and the rectangular pattern region formed on the mask includes terminal regions in at least one external portion of its long side direction in order to respectively arrange the drive signal lines in least one of its terminal regions dividing the terminal regions into respective rectangular pattern regions corresponding to the projected first image and second image stitch exposed together.
In another embodiment of the present invention, the dimension in the short side direction of the rectangular pattern region is made of a single integral part of the width of the terminal region.
In another embodiment of the present invention, the whole exposure range of the non-scanning direction is perpendicular to the direction of scanning exposure so as to include the dimension of the short side direction of the rectangular pattern region, and multiple projection optical systems are adjacently positioned along the non-scanning direction to scan expose within the respective visual fields of these plural projection optical systems and limiting the specific visual fields according to the dimension of the short side direction of the rectangular pattern region.
In another embodiment of the present invention, the whole exposure range in the non-scanning direction has an arcuate slit shaped visual field that includes the dimension in the short side direction of the rectangular pattern region, wherein the arcuate slit-shaped visual field restricts the scanning exposure according to the dimension in the short side direction of the rectangular pattern region.
In another embodiment of the present invention, a circuit pattern for a display device is formed on the mask and is applied to manufacture a large size display device by stitch exposure on a plate, where the size of the display picture surface is 30 inches or more in the horizontal direction, and is divided in the horizontal direction into regions with each region formed by stitch exposing a circuit pattern on the plate by a scanning exposure device, where the long side direction of the respective divided regions is the direction of scanning movement of the plate by the scanning exposure device, and the short side direction of the respective divided regions is the direction of a horizontal scan line (HL) of the display picture surface and is set smaller than the maximum range of the projection visual field with respect to the non-scanning direction of the scanning exposure device.
In another embodiment of the present invention, the scanning exposure device is equipped with a mask stage that moves the mask at a roughly uniform speed during scanning exposure, reduces the dimension in the long side direction of the respective divided region, and is capable of fine movement in the non-scanning direction and fine rotation around an axis perpendicular to the surface of the mask, and a plate stage that supports the plate and moves at a uniform speed in the direction corresponding to the horizontal line (HL) of the display picture surface, and steps/moves in a direction corresponding to the horizontal line (HL) of the display picture surface.